Hydrocracking nitrogen-containing feed in the presence of halides



Feb. 2l, 1967 R. A. PEcK ETAL HYDROCRACKING NITROGEN-CONTAINING FEED INTHE PRESENCE OF HALIDES Filed July 17, 1964 www ll Nm,

AAJ' @mi United States Patent Oilice 3,305,477 Patented Feb. 2l, 19673,305,477 HYDROCRACKING NITROGEN-CONTAINING FEED IN THE PRESENCE FHALIDES Reese A. Peck, Fishkill, Donald A. Messing, Glenham, and EdwinR. Kerr, Wappingers Falls, N.Y., assignors to Texaco inc., New York, N.Y., a corporation of Delaware Filed July 1'7, 1964, Ser. No. 383,315 8Claims. (Cl. 208-112) This invention relates to the conversion ofhydrocarbons. More particularly it is concerned with the conversion ofhydrocarbons in the presence of hydrogen to lighter hydrocarbons. In itsmost specific aspects it is concerne-d with the conversion of a nitrogencontaining hydrocarbon feed stock boiling approximately in thekerosine-gas oil range in the presence of hydrogen and a crackingcatalyst into hydrocarbons boiling in the naphthakerosine range.

Hydrocracking, previously known as destructive hydrogenation, has becomeinto prominence recently in the refining of petroleum hydrocarbons. Inthe hydrocracking process various reactions take place such as thecleaving of long straight carbon chains, the saturation of aromaticrings with subsequent rupture of cycloparainic structure, theisomerization of paraiiinic chains into isoparainic chains and thedealkylation of alkyl aromatics. Ordinarily, the charge to ahydrocracking unit will comprise hydrocarbons boiling above the range ofthe desired product. For example, if a motor fuel is desired, the chargeto the hydrocracking unit will have an initial boiling point of about40G-450 F. whereas if the desired products are -motor fuels and jetfuels, then the charge to the hydrocracking unit will have an initialboiling point of S50-600 F. Advantageously, charge stocks such asstraight run kerosine and gas oil stocks from catalytic cracking, vacuumgas oil and light distillates obtained from coal and shale maybe chargedto the hydrocracking unit. Ordinarily, product boiling above the desiredend point is recycled to the hydrocracking unit.

HydrocrackingV is preferably carried out in the presence of a catalystwhich generally contains two'components,`

a hydrogenating component and a cracking component. Numeroushydrogenating components have been disclosed in the prior art such asGroup VIII metals for example platinum, palladium and nickel and theoxides and suldes of molybdenum, nickel, copper, tungsten, and cobalt,and the like or mixtures thereof. The hydrogenating component issupported on a cracking base which advantageously is acidic in nature.Such bases comprise refractory oxides of two or more elements of GroupsII, III, and IV of the periodic table. Suitable cracking supportsinclude silica-magnesia, silica-alumina, silicaalumina-zirconia and thelike. Preferably the cracking support is activated by treatment with aninorganic acid such as hydrouoric acid or hydrochloric acid. The presentinvention is particularly concerned with the use of catalysts comprisingas the hydrogenating component the oxide and/or sulfide of cobalt ornickel supported on a silica-alumina cracking base.

While these catalysts are eminently suitable for hydrocracking ofVarious petroleum charge stocks, they are subject to an acute loss ofcatalyst activity when the charge stock contains even relatively smallamounts of nitrogen. As a measure of the catalyst activity, it iscustomary to institute a hydrocracking reaction and conduct the processat certain conditions of temperature, pressure,

' space velocity and hydrogen rate to maintain a predeterminedconversion of the charge into 4material having a particular end boilingpoint.v As the reaction proceeds, the catalyst is subject to loss inactivity and to compensate for the reduced activity the temperaure inthe catalytic zone is increased to maintain a constant conversion rate.This increase in temperature necessary to maintain the desiredconversion is called` the aging rate. For example, it has been foundthat in a particular run when the charge contained 10 p.p.rn. nitrogen,the aging rate was 24 F. per 100 hours. In the treatment of a similarcharge containing only 3 p.p.m. nitrogen the aging rate was 7 F. per 100hours and with a charge containing 1 p;p.m. nitrogen the aging rate was2.4 F. per 10() hours. When hydrocracking to produce a high octane motorfuel, the reactions which result in the desired type of product areinhibited after the temperature in the hydrocracking unit has reachedabout 775 F. It therefore becomes apparent that a charge stock whichcontains even as much as l0 p.p.m. nitrogen produces an undesirablyrapid decline in catalyst activity. As a result a charge stock destinedfor treatment in a hydrocracking unit either must be subjected to rathersevere treatment or the process must pay an excessive economic penalityin the way of frequent catalyst regeneration.

It has now been discovered that by the simple practice of subjecting thecharge stock destined for the hydrocracking unit to a mild rather thansevere hydrogenation thereby reducing the nitrogen content of the chargestock into'the area of 5-20 ppm. nitrogen rather than the 0-2 p.p.m. ofthe prior art and adding an organic halide to the hydrogenation product,the life of the catalyst in the hydrocracking unit is'extendedconsiderably beyond the period that would normally be expected whencharging a material of such a high nitrogen content. lAlternatively thehydrocracking unitmay be operated at a lower temperature for thesamedegree of conversion that would lbe obtained if the charge has beensubjected to a severe denitrication treat-ment prior to being introducedinto the hydrocracking unit.

It is an object of the present invention to provide a process for thehydrocracking of a hydrocarbon charge stock containing more than about 2p.p.'m. nitrogen.

It is a further object of this invention to prolong the life of ahydrocracking catalyst.

Itis a still further object of this invention to provide a two-stageprocess in which .a nitrogen containing charge stock is subjected to a.mild denitrogenation treatment, an organic halide is added to theso-treated material and the mixture is subjected to theaction of ahydrocracking catalyst comprising nickel `or cobalt. These and otherobjects will be obvious to those skilled in the art from the followingdisclosure.

The catalysts used in the hydrocracking process of th present inventioncomprise a hydrogenating component such as an oxide and/ or sulfide ofcobalt and/or nickel supported on an acidic base such as silica aluminaor silica magnesia. Optionally, the catalyst is treated with HF or HCL.

The hydrogen used in the present process may be suitpure hydrogen.

The reaction conditions within the hydrocracking unit generally includea temperature range from about 450- 800 F. although a temperature from500 to about 750- 775 F. is preferred. Pressure will range from aboutSOO-10,000 p.s.i.g. or higher although a pressure of from about 1,000 to3,000 p.s.i.g. is preferred. The hydrogen rate may range from 1,000 toabout 20,000 s.c.f.b. (Standard cubic feet per barrel) of normallyliquid charge. Preferred hydrogen rates are from about 3,000-8,000s.c.f.b. Preferably the space velocity, that is the volumes of liquidcharge per volume of 4catalyst per hour, will be between 0.5 and 3although rates ranging from 0.1-10 may be used.

If the charge stock to the hydrocracking unit contains not more thanabout 2-20 p.p.m. nitrogen it may be charged directly to thehydrocracking unit. Preferably as in the case of higher nitrogencontaining stocks, the hydrocarbon feed is first charged to adenitrogenation zone where it is contacted with a catalyst such as amixture of oxides of cobalt and molybdenum generally referred to ascobalt molybdate on a support such as magnesia or alumina. Suitableother catalysts comprise the oxides or sulfides or mixtures thereof ofmetals such as nickel, molybdenum, cobalt, tungsten and the like, forexample sulfided nickel tungsten on alumina or a mixture of nickel andmolybdenum in either the oxide or the sulde form on alumina.Satisfactory denitrogenation temperatures include a range of 700-900 F.,a pressure of 100-5,000 p.s.i.g., a space velocity of 0.1-10, and ahydrogen rate of from SOO-10,000 s.c.f.b.

In the two-stage denitrogenation and hydrocracking operation each stagemay have its own hydrogen circulation system or the hydrogen maycirculate serially through both reaction zones. However, if the hydrogenfrom the denitrogenation zone is to be used in the hydrocracking zone,it is subjected to a basic nitrogen removal treatment as for example bywashing with dilute acid. The charge to the hydrocracking unit afterremoval from the denitrogenation zone is advantageously stripped with aninert gas for the removal of nitrogen compounds such as ammoniatherefrom. Apparently, the use of molecular nitrogen as a stripping gas,even though it is retained to the extent of 100 p.p.m. in the strippedhydrocracking unit charge stock, exerts no deleterious effect on thehydrocracking catalyst. The denitrogenation treatment also effectivelyremoves oxygen containing compounds from the charge.

Halogen is added to the charge to the hydrocracking unit in the form ofan organic halide such as an alkyl or laryl halide. Preferably thosehalides having a high halogen content as utilized although the inventionis not limited thereto. Satisfactory results are obtained by theaddition of dichloroethanes, carbon tetrachloride, tertiary butylchloride and the like. The organic halide is added to the charge to thehydrocracking unit in an amount suicient to proivde a halogenconcentration of at least 1 atom of halogen per atom of nitrogen in thecharge stock. Preferably at least `l atoms of halogen are supplied peratom of nitrogen. Ordinarily, no apparent advantage is to be gained bysupplying halogen in an atomic ratio in excess of about 300.

It is a feature of the present invention that when the hydrogenatingcomponent of the hydrocracking catalyst consists essentially of theoxide or sulde of nickel or cobalt, no moisture or water need be addedto the charge to the hydrocracking unit. iIn other words, thehydrocracking is carried out essentially under anhydrous conditions.Conventionally, the charge to the hydrocracking unit is subjected to lapreliminary denitrogenation treatment or if its nitrogen content issufficiently low is sent to the hydrocracking unit from a crude still orfrom a catalytic cracking unit, Under these circumstances the charge tothe hydrocracking unit will be free from water or will contain water inthe range of about 0-4 parts per million. Accordingly, in the a-bsenceof added water it will be appreciated that the hydrocracking process ofthe present invention is carried out under essentially anhydrousconditions.

For a better understanding of the process of the present inventionreference is now made to the accompanying 4 drawing which showsdiagrammatically a flow scheme for the practice of a preferredembodiment of the invention.

The nitrogen containing hydrocarbon charge stock is introduced into thesystem through line 12 and with hydrogen from line 14 passes intohydrogenation reactor 15 where it is subjected to hydrodenitrogenationconditions. Effluent from hydrogenation reactor 15 is transferred bymeans of line 16 to high pressure separator 17 where a vapor liquidseparation is made, the vapors being sent to gas scrubber 19 throughline 18 and the liquid being sent to liquid stripper 21 through line 22.

A scrubbing liquid such as for example, dilute sulfuric acid isintroduced through line 25 into gas scrubber 19 and effectively removesimpurities such as ammonia from the gas stream, the scrubbing liquid andimpurities being withdrawn through line 26. In liquid stripper 21 theliquid porton of the hydrogenation product is subjected tocounter-current stripping `with an inert gas such as nitrogen introducedthrough line 28 and removed through line 30. This stripping operationserves to remove entrained gases such as low molecular weighthydrocarbons, ammonia and, if present, hydrogen sulfide. The strippedliquid then passes through line 32 to fractionator 34 from which naphthais removed through line 35. The heavier than naphtha liquid is then sentthrough -line 37 and with purified hydrogen from line 38 is introducedinto hydrocracking reactor 40. Organic halide `is injected into thehydrocarbon stream through line 42. Efiuent from hydnocracking reactor40 ows through line 45 to high pressure separator 46 from which ahydrogen rich stream is recycled through lines 14 and 12 tohydrogenation reactor 15 and from which liquid product is sent throughline 47 to fractionator 50. Fractionator 50 may in actual practiceinclude several vessels but is depicted here as a single unit which isused to separate t-he liquid product into various fractions which mayibe removed through lines 51 and 52, respectively. Heavy hydrocarbonsboiling above the desired product may be recycled to hydrocrackingreactor 40 through lines 53, 37 and 38.

Make-up hydrogen as required may be introduced into the system dependingon its purity either through line 54 or 56. If the make-up |hydrogen isof high purity advantageously it is introduced through line 54. Howeverif the make-up hydrogen is of low purity or contains undesirablecomponents such as nitrogen then it is introduced into the systemthrough line 56. Although serial flow of Ihydrogen is shown, thehydrogen passing rst through the hydrogenation reactor and then thehydrocracking reactor it is possible for each reactor to have its ownhydrogen circulation system.

Obviously, various items of equipment such as heaters, valves, pumps,compressors and the like have been omitted from the drawing for the sakeof simplicity.

T'he process of the present invention finds its most advantageousapplication in prolonging the life of a hydrocracking catalyst when thecharge stock contains up to about 10 p.p.m. nitrogen. Referring back tothe charges mentioned above having nitrogen contents of l0, 3 and lp.p.m. nitrogen respectively and corresponding aging rates of 24 F., 7F. and 2.4 F. respectively per 100 hours, it is obvious that inconventional hydrocracking processes the catalyst life is indirectlyproportional to the nitrogen content of the charge stock. The catalystlife ordinarily is measured in terms of the AT of the run, that is thedifference between the starting temperature and the ternperature at theend of the run. Over a AT of 200 F. hydrocracking at a constantconversion rate of the above essentially anhydrous (less than l0 ppm.H2O) charge stocks results in catalyst lives of 1.15, 4 and 11.5 monthsrespectively.

By way of example, an intermediate cycle gas oil obtained from a uidcatalytic cracking unit after being subjected to a mild denitrogenationand containing 8 p.p.m. H2O and 4 p.p.rn. nitrogen has an aging rate of8.7" F. per hours or a life of 3.2 months using a catalyst comprisingapproximately 5% nickel on a base containing 11.4% alumina and 83.6%silica. When this same charge is hydrocracked under substantially thesame operating and conversion conditions in the absence of addedmoisture but in the presence of 800 p.p.m. 1,1-dichloroethane, the agingrate is 3.4 F. per 100 hours which is translated into a catalyst life of8.2 months.

Obviously, many modifications and variations of the invention ashereinbefore set forth may be made without departing Ifrom the spiritand scope thereof and therefore only such limitations should be imposedas are indicated in the appended claims.

We claim:

1. A process for the hydrocracking of a hydrocarbon charge stock boilingwithin the range of about 400-800" F. and containing at least about 3p.p.m. nitrogen which comprises contacting said charge stock with acatalyst comprising a hydrogenating component selected from the groupconsisting of oxides and suldes of nickel and cobalt supported on anacidic cracking base at a temperature between about 450 and 800 F., apressure between about 500 and 10,000 p.s.i.g. in the presence ofbetween about 1,000 and 20,000 s.c.f. hydrogen per barrel of chargethere being added to said charge an organic halide in an amountsuiicient to provide at least atoms of halogen per atom of nitrogen insaid charge stock.

2. The process of claim 1 in which the hydrogenating component comprisesnickel oxide.

3. The process of claim 1 in which the hydrogenating component comprisesnickel sulfide.

4. The process yof claim 1 in which the hydrogenating componentcomprises cobalt oxide.

5. The process of claim 1 in which the hydrogenating component comprisescobalt sulfide.

6. The process of claim 1 in which the hydrocracking is carried out inthe absence of added water.

7. The process for the hydrocracking `of an essentially anhydroushydrocarbon charge stock boiling Within the range of about 400-800 F.and containing between 3 and l0 p.p.m. nitrogen which comprisescontacting said charge stock in the absence of added moisture with acatalyst comprising a 'hydrogenating component selected from the groupconsisting of oxides and sulfides of nickel and cobalt supported on anacidic cracking base at a temperature between about 450 and 800 F., apressure between about 500 and 10,000 p.s.i.g. in the presence ofbetween about 1,000 and 20,000 s.c.f. hydrogen per barrel of charge,there being added to the hydrocracking zone an organic halide in anamount suicient to provide at least 10 atoms of halogen per atom ofnitrogen in said charge stock.

8. The process of claim 7 in which the atomic ratio of halogen tonitrogen is between 10 and 300.

References Cited by the Examiner UNITED STATES PATENTS 3,047,490 7/ 1962Myers 208-59 3,072,560 1/1963 Paterson et al 208-111 3,213,012 10/1965Kline et al 208-111 DELBERT E. GANTZ, Primary Examiner.

S. P. JONES, Assistant Examiner.

1. A PROCESS FOR THE HYDROCRACKING OF A HYDROCARBON CHARGE STOCK BOILING WITHIN THE RANGE OF ABOUT 400-800* F. AND CONTAINING AT LEAST ABOUT 3 P.P.M. NITROGEN WHICH COMPRISES CONTACTING SAID CHARGE STOCK WITH A CATALYST COMPRISING A HYDROGENATING COMPONENT SELECTED FROM THE GROUP CONSISTING OF OXIDES AND SULFIDES OF NICKEL AND COBALT SUPPORTED ON AN ACIDIC CRACKING BASE AT A TEMPERATURE BETWEEN ABOUT 450 AND 800*F., A PRESSURE BETWEEN ABOUT 500 AND 10,000 P.S.I.G. IN THE PRESENCE OF BETWEEN ABOUT 1,000 AND 20,000 S.C.F. HYDROGEN PER BARREL OF CHARGE THERE BEING ADDED TO SAID CHARGE AN ORGANIC HALIDE IN AN AMOUNT SUFFICIENT TO PROVIDE AT LEAST 10 ATOMS OF HALOGEN PER ATOM OF NITROGEN IN SAID CHARGE STOCK. 